01 Introduction University of

							University of Central Punjab

     CS1204 – Lecture 1

             Introduction

            Prof. Engr. Ahmed Hafeez
        Faculty of Information Technology
  In Learning THE PROCESS is more
    important then THE RESULTS!
• Problem solving techniques and skills can only be acquired
  through practice and through the study of increasingly more
  difficult problems. The assignments all involve problem
  solving. It is very important that you understand how you
  solved the problem.
• HOW – is more important then DO
• After graduation: No one will ask you about your grades!
  Everyone will ask if you can solve problems
• This requires individual study – beyond class and Lab.
• I cannot learn for you! (SORRY…)
• I will do my very best to help you through THE PROCESS!
           HOW TO SUCCEED
• DO THE LAB EXERCISES AND ALL THE
  ASSIGNMENTS!
• DO EXTRA EXERCISES (basis for
  understanding!) 10% inspiration – 90% practice!
• WE WILL LEARN TOGETHER HOW TO
  THINK. Capture the essence about the topic – so
  you can solve similar problems based on what you
  learned!) – [Thinking – vs. memorizing…].
• PARTICIPATE!
• Ask for help!
Ground Rules (so the Process runs best)
• Cellular phones „OFF‟ during class
• No side talking during class
• Write your questions and ask them when I invite you
  to do so
• ?? What do you wish to add…
• Ground Rules are negotiable – but only before they
  are broken
          Digital Electronics
• Digital Electronics represents information (0, 1) with
  only two discrete values.
• Ideally
      “no voltage” (e.g., 0v) represents a 0 and
      “full source voltage” (e.g., 5v) represents a 1
• Realistically
      “low voltage” (e.g., <1v) represents a 0 and
      “high voltage” (e.g., >4v) represents a 1
• We achieve these discrete values by using switches.
• We use transistor switches, which operate at high speed,
  electronically, small in size.
           Analog versus Digital

• Analog systems process time-varying signals that
  can take on any value across a continuous range
  of voltages (in electrical/electronics systems).
• Digital systems process time-varying signals that
  can take on only one of two discrete values of
  voltages (in electrical/electronics systems).
  – Discrete values are called 1 and 0 (ON and OFF,
    HIGH and LOW, TRUE and FALSE, etc.)
 Representing Information Electronically

• A light bulb has to represent 4 different
  information:
  Bulb off -        no student inside
  Bulb 1/3 lit -    1 student inside
  Bulb 2/3 lit -    2 student inside
  Bulb Full lit -   3 student inside


• A light bulb has to represent 10 different
  information:
  – Is it possible to differentiate the ten different light
    intensity?
 Representing Information Electronically
• A light bulb has to represent 2 different information:
   Bulb off -         no student inside
   Bulb Full lit -    1 student inside


• A light bulb has to represent 4 different information:
   – How? With one bulb?
   – Use two bulbs


• A light bulb has to represent 10 different information:
   – Use four bulbs
 Representing Information Electronically
• “Analog electronics” deals with non-discrete values

• “Digital electronics” deals with discrete values
      Benefits of Digital over Analog
•   Reproducibility
•   Not effected by noise means quality
•   Ease of design
•   Data protection
•   Programmable
•   Speed
•   Economy
        Digital Devices

•Gates
•Flip-Flops
•PLDs
•FPGAs
                     Gates
• The most basic digital devices are called gates.
• Gates got their name from their function of
  allowing or blocking (gating) the flow of digital
  information.
• A gate has one or more inputs and produces an
  output depending on the input(s).
• A gate is called a combinational circuit.
• Three most important gates are: AND, OR, NOT
               Digital Logic
• Binary system -- 0 & 1, LOW & HIGH.
• Basic building blocks -- AND, OR, NOT
AND, OR, NOT Gates
                    Flip-flops
• A device that stores either a 0 or 1.
• Stored value can be changed only at certain times
  determined by a clock input.
• New value depend on the current state and it‟s
  control inputs
• A digital circuit that contains flip-flops is called a
  sequential circuit
                    Flip-flops



S-R latch symbols                    D flip-flop




                    J-K flip-flops
              Integrated Circuits
• A collection of one or more gates fabricated on a
  single silicon chip is called an integrated circuit
  (IC).
• ICs were classified by size:
  –   SSI - small scale integration - 1~20 gates
  –   MSI - medium scale integration - 20~200 gates
  –   LSI - large scale integration - 200~200,000 gates
  –   VLSI - very large scale integration - over 1M
      transistors
• Pentium-IV - 55 million transistors
DIP Packages
Gates in ICs
     Programmable Logic Devices
• PLDs allow the function to be programmed into
  them after they are manufactured.
• Complex PLDs (CPLD) are a collection of PLDs
  on the same chip.
• Another programmable logic chip is FPGA -
  field-programmable gate arrays.
  CPLDs and FPGAs
CPLD                FPGA
   Application Specific ICs (ASICs)
• Chips designed for a particular application are
  called semicustom ICs or application-specific ICs
  (ASICs).
• ASICs generally reduce the total component and
  manufacturing cost of a product by reducing chip
  count, physical size, and power consumption, and
  they often provide higher performance.
• But costly if not produced in bulk.
         Printed-Circuit Boards
• An IC is normally mounted on a printed-circuit
  board (PCB) that connects it to other ICs in a
  system.
• Individual wire connection or traces can be as
  narrow as 4 mils with 4 mils spacing (one-
  thousandth of an inch)
• Now a days, most of the components use surface
  mount technology.
• They are normally layered.
Software Aspects of Digital Design
• Today software tools are an essential part of digital
  design.
• Software tools improve productivity, correctness and
  quality of designs
• Software tools are:
   – Schematic entry
   – HDL (Hardware Description Language) Editors
   – Simulators - to verify the behaviour of the design
   – Synthesis tools - circuit design
   – Timing analyzers and verifiers
           Digital Design Levels
• the lowest level of design is device physics and
  IC manufacturing processes.
• design at the transistor level
• level of functional building blocks
• level of logic design using HDLs
• computer design and overall system design.
          Different Design Levels
Consider a simple design example:

Build a multiplexer with two data inputs A and B, a
control input S, and an output Z.




        Switch model for the example multiplexer
   Designing at the transistor level
• Transistor-level
  circuit diagrams




• Gate symbols (for simple elements)
• Logic design
  using Truth tables
• Logic design
  using boolean algebra
     Equations: Z = S A + S  B



• Logic diagrams
• Prepackaged building blocks, e.g. multiplexer
  Structural HDL program for the multiplexer
 ________________________________________
//Dataflow description of 2-to-1-line multiplexer
module mux2x1_df (A,B,select,OUT);
  input A,B,select;
  output OUT;
  assign OUT = select ? A : B;
endmodule
_________________________________________
                    Summary
•   Design to minimize cost.
•   Rule of thumb is to minimize the number of ICs.
•   Though PLDs costs more but uses less PCB area.
•   Unless mass production avoid ASIC design.
•   Design to solve real life problems.